package com.journey.web.util;

import org.springframework.http.HttpInputMessage;
import org.springframework.http.HttpOutputMessage;
import org.springframework.http.MediaType;
import org.springframework.http.converter.AbstractHttpMessageConverter;
import org.springframework.util.FileCopyUtils;

import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.UnsupportedEncodingException;
import java.nio.charset.Charset;
import java.util.ArrayList;
import java.util.List;

/**
 *  重写SpringMVC的字符串转换器，使用UTF-8编码
 * @author journey
 * @date 2017-03-15
 *
 */
public class UTF8StringHttpMessageConverter extends AbstractHttpMessageConverter<String> {
      
    public static final Charset DEFAULT_CHARSET = Charset.forName("UTF-8");
      
    private final List<Charset> availableCharsets;
      
    private boolean writeAcceptCharset = true;  
      
    public UTF8StringHttpMessageConverter() {  
        super(new MediaType("text", "plain", DEFAULT_CHARSET), MediaType.ALL);  
        this.availableCharsets = new ArrayList<Charset>(Charset.availableCharsets().values());
    }  
      
    /** 
     * Indicates whether the {@code Accept-Charset} should be written to any outgoing request. 
     * <p> 
     * Default is {@code true}. 
     */  
    public void setWriteAcceptCharset(boolean writeAcceptCharset) {  
        this.writeAcceptCharset = writeAcceptCharset;  
    }  
      
    @Override
    public boolean supports(Class<?> clazz) {
        return String.class.equals(clazz);
    }  
      
    @SuppressWarnings("rawtypes")
    @Override
    protected String readInternal(Class clazz, HttpInputMessage inputMessage) throws IOException {
        Charset charset = getContentTypeCharset(inputMessage.getHeaders().getContentType());
        return FileCopyUtils.copyToString(new InputStreamReader(inputMessage.getBody(), charset));
    }  
      
    @Override
    protected Long getContentLength(String s, MediaType contentType) {
        Charset charset = getContentTypeCharset(contentType);
        try {  
            return (long) s.getBytes(charset.name()).length;  
        } catch (UnsupportedEncodingException ex) {
            // should not occur  
            throw new InternalError(ex.getMessage());
        }  
    }  
      
    @Override
    protected void writeInternal(String s, HttpOutputMessage outputMessage) throws IOException {
        if (writeAcceptCharset) {  
            outputMessage.getHeaders().setAcceptCharset(getAcceptedCharsets());  
        }  
        Charset charset = getContentTypeCharset(outputMessage.getHeaders().getContentType());
        FileCopyUtils.copy(s, new OutputStreamWriter(outputMessage.getBody(), charset));
    }  
      
    /** 
     * Return the list of supported {@link Charset}.
     * <p> 
     * By default, returns {@link Charset#availableCharsets()}. Can be overridden in subclasses.
     * @return the list of accepted charsets 
     */  
    protected List<Charset> getAcceptedCharsets() {
        return this.availableCharsets;  
    }  
      
    private Charset getContentTypeCharset(MediaType contentType) {
        if (contentType != null && contentType.getCharSet() != null) {  
            return contentType.getCharSet();  
        } else {  
            return DEFAULT_CHARSET;  
        }  
    }  
      
}  